This invention relates to an apparatus and method of molding an article wherein a portion of the article is blow molded and another portion is compression molded.
Blow molding processes are widely used to form hollow articles from plastic materials. Generally, a parison, which is a generally tubular blank of molten plastic material, is extruded from a suitable extrusion head and is allowed to drop by gravity into the interior of a mold. After upper and lower ends of the parison are sealed off by, for example, closing two mold parts upon the parison, a compressed gas such as air is injected into the parison to pneumatically expand the parison to fit the inside contours of the mold.
It is occasionally desirable to compression mold a portion of an article which is being blow molded. Such a need can arise, for example, in hollow articles which require an associated high strength, protruding member.
Prior techniques of combining blow molding and compression molding have been used with some success, but improvement would be desirable.